Hopefully he's eaten by now? It's 3 days since your post. Generally you should keep a puppy on the food he is used to when you first get him, a whole big bag at least or a couple of months. Many of the changes inflicted on puppy you can't control but you can at least keep his food the same and hopefully avoid the unpleasant reactions that sometimes accompany a food change. But you can't be sure if the food you were told to get is really what he was on. Plus, even if it is, he might have been on it only a very short time.
Are you letting him settle in? It's not a good idea to allow all your friends and neighbours in right away or to take him out to many places. You want to do those things, yes, for socialization, but he needs to settle and feel safe too. For a couple of days at least, to maybe a week, keep visits in and out to a minimum.